System and method for control of fan rotational speed

ABSTRACT

A system and a method for control of fan rotational speed are applied in an electronic device with a fan for temperature adjustment. The electronic device at least records a first fan rotational speed of the fan when a temperature of the fan is higher than a predetermined temperature interval and a second fan rotational speed of the fan when the temperature of the fan is lower than the temperature interval. A fan rotational speed during operation of the fan is recorded. The electronic device detects a temperature of an exothermic object being adjusted by the fan, and outputs a temperature parameter. The electronic device determines whether the temperature parameter belongs to the temperature interval and accordingly adjusts the fan rotational speed of the fan. The system and method make change of the fan rotational speed less sensitive to oscillations in system temperature and prolong the lifetime of the fan.

FIELD OF THE INVENTION

The present invention relates to systems and methods for control of fanrotational speed, and more particularly, to a system and method forcontrol of fan rotational speed of a fan according to a predeterminedtemperature interval.

BACKGROUND OF THE INVENTION

Computers have become indispensable tools during work and everyday life,and technological advances have brought about increases in theoperational speed of the central processing unit (CPU) which allow theexecution of more and more processor-intensive programs. However, a hugeamount of heat energy is generated when a CPU is operated at high speed,which, in turn, has a considerable effect on the system. Minor effectsinclude temporary system hangs, and major effects include unrecoverabledisk or processor damage to the system. Thus, research into systemheat-radiating ability is receiving more and more attention.

Cooling through the use of a fan is the most commonly used radiatingmethod in the market. This kind of radiating device is constructed of afan and a heat sink device equipped with fins. This device is broadlyapplied in computer systems and other electronic devices based on itsadvantages of simple structure, low cost, safety, reliability, technicalmaturity, and so on. In order to quickly radiate a large amount of heatenergy generated by the system heat sources, the rotational speed of thesystem radiating fan has to be accelerated. However, additional noise isgenerated by higher rotational speeds. In addition, regularly rotatingthe fan at high speed reduces its lifespan.

In order to solve the problem mentioned above, a fan rotational speedcontrol technique has appeared in the market. A temperature sensingdevice is utilized, wherein, according to the changes of systemtemperature, the fan rotational speed will also be altered. In thistechnique, the fan is operated in at least a low-speed rotation mode anda high-speed rotation mode. FIG. 1 illustrates how the fan rotationalspeed is controlled based on a critical temperature value. As shown inthe diagram, the temperature changing curve 10 illustrates an electronicdevice (e.g. computer main frame, laptop, etc) with an installedtwo-speed fan (in addition to off). The critical temperature value isdenoted as Ct and shown by the dashed, horizontal line. Systemtemperature varies above and below this critical temperature dependingon system utilization and environmental factors. As illustrated by thefan rotational speed line 12 in the diagram, when the system temperatureexceeds the critical temperature value, the fan rotational speedcontroller will adjust the fan rotational speed into the high-speedrotation mode. Conversely, when the temperature drops below the criticaltemperature value, the fan rotational speed controller will adjust thefan rotational speed into the low-speed rotation mode. However, thepresent fan rotational control speed technique is still lacking. Inparticular, when the system temperature oscillates around the criticaltemperature value, the fan rotational speed controller has tocontinually respond and adjust the fan rotational speed in order to meetthe requirements. Such frequent changes of the fan rotational speed willresult in a shorter fan life.

In order to solve the deficiency mentioned above, an improvement schemeis proposed. As shown in FIG. 2, the amount of a predeterminedinsignificant temperature change Δt is deducted from the criticaltemperature value Ct to form a second critical temperature value Ct₁. Acritical temperature interval exists between the critical temperaturevalue Ct and the critical temperature value Ct₁, that is the criticaltemperature value Ct is the upper limit and the other criticaltemperature value Ct₁ is the lower limit (the difference of Ct minus theinsignificant temperature change Δt). When the system temperatureexceeds the critical temperature value Ct, the fan rotational speedcontroller adjusts the fan into the high-speed rotation mode. When thetemperature drops below the critical temperature value Ct minus theinsignificant temperature change Δt to the critical temperature valueCt1, the fan rotational speed controller will adjust the fan into thelow-speed rotation mode. Using this technique, the fan can be kept at astable speed for a longer time. However, this method cannot fully solvethe problem of frequent rotational speed changes caused by oscillatingtemperature. As shown in the diagram, when the system temperature changecurve 20 oscillates around the critical temperature value Ct₁, suddenabrupt changes of the fan rotational speed will still occur. A suddenabrupt rotational speed change 220 can occur as shown by the fanrotational speed change line 220 at the relative points, and thelifespan of the fan will be degraded.

For this reason, a system and a method for control of fan rotationalspeed is needed to avoid the deficiency of the previously mentionedtechnique, thus making the change of the fan rotational speed lesssensitive to temperature oscillations, and hence remarkably prolongingthe life of the fan, as well as reducing system noise.

SUMMARY OF THE INVENTION

In order to solve the problems of the prior art, a primary objective ofthe present invention is to provide a system for control of fanrotational speed that avoids repetitive changes of the fan rotationalspeed in a short period of time due to system temperature oscillations.

Another objective of the present invention is to provide a method forcontrol of fan rotational speed that achieves the objectives of savingpower and prolonging the life of the fan.

In order to achieve the above objectives, the system for control of fanrotational speed is applied in the electronic device with a built-in fanfor temperature adjusting purposes. The system includes at the veryleast: a temperature interval recording module for at least recordingthe relative first fan rotational speed when the temperature is at leasthigher than a temperature interval and the relative second fanrotational speed when the temperature is lower than the temperatureinterval; a rotational speed recording module for recording the fanrotational speed when the fan is operating; a temperature detectingmodule for detecting the temperature of an exothermic object beingadjusted by the fan and for outputting temperature parameters; and adetermining module for determining whether the temperature parameteroutputted by the temperature detecting module belongs to the temperatureinterval recorded by the temperature interval recording module andsending control signals accordingly. For the determining module, if thetemperature parameter belongs to the temperature interval, the systemkeeps the same rotational speed for the fan operation, and, if thetemperature parameter does not belong to the temperature interval, thenaccording to the temperature parameters of the temperature intervalrecording module, it determines whether the relative fan rotationalspeed is the same as the fan rotational speed recorded in the rotationalspeed recording module. If the fan rotational speeds are not the same,according to the temperature parameter of the temperature intervalrecording module, it determines whether the temperature parameter islower than the temperature interval. If the temperature parameter islower, it slows down the fan rotational speed and then updates the fanrotational speed recorded in the rotational speed recording module withthe latest fan rotational speed. On the contrary, if the temperatureparameter is higher, it operates the fan with the rotational speedrecorded in the rotational speed recording module. In contrast, if thefan rotational speeds are the same, then, according to the temperatureparameter of the temperature interval recording module, it determineswhether the temperature parameter is higher than the temperatureinterval. If the temperature parameter is higher, it speeds up the fanrotational speed and then updates the fan rotational speed recorded inthe rotational speed recording module with the latest fan rotationalspeed. On the contrary, if the temperature parameter is lower, itoperates the fan with the rotational speed recorded in the rotationalspeed recording module.

The method for control of fan rotational speed is applied in anelectronic device with a built-in fan for temperature adjustingpurposes. The method at the very least includes the followingprocedures: making the electronic device at least record the relativefirst fan rotational speed when the temperature is at least higher thana temperature interval and the relative second fan rotational speed whenthe temperature is lower than the temperature interval, and recordingthe fan rotational speed when the fan is operating; making theelectronic device detect the temperature of an exothermic object beingadjusted by the fan, and outputting the temperature parameters; andmaking the electronic device determine whether the output temperatureparameter belongs to the temperature interval recorded by thetemperature interval recording module. If the temperature parameterbelongs to the temperature interval, the method keeps the samerotational speed for the fan operation. If the temperature parameterdoes not belong to the temperature interval, then, according to thetemperature parameter, it determines whether the relative fan rotationalspeed is the same as the recorded fan rotational speed. If the fanrotational speeds are not the same, then, according to the temperatureparameter, it determines whether the temperature parameter is lower thanthe temperature interval. If the temperature parameter is lower, itslows down the fan rotational speed and then updates the fan rotationalspeed recorded in the electronic device with the latest fan rotationalspeed. On the contrary, if the temperature parameter is higher, itoperates the fan with the rotational speed recorded in the electronicdevice. In contrast, if the fan rotational speeds are the same, then,according to the temperature parameter, it determines whether thetemperature parameter is higher than the temperature interval. If thetemperature parameter is higher, it speeds up the fan rotational speedand then updates the fan rotational speed recorded in the electronicdevice with the latest fan rotational speed. On the contrary, if thetemperature parameter is lower, it operates the fan with the rotationalspeed recorded in the electronic device.

Compared with the commonly used fan rotational speed control technique,sudden abrupt changes of fan rotational speed caused by the temperatureoscillation can be avoided, according to the preset temperature intervalof the system and the method for control of fan rotational speed of thepresent invention, so as to avoid the deficiency of the prior art,smooth the fan operational rotational speed, prolong the life of thefan, and reduce system noise.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when theforgoing detailed description is considered in conjunction with thefollowing drawings, in which:

FIG. 1 (PRIOR ART) is a diagram showing the commonly used criticaltemperature method for control of fan rotational speed;

FIG. 2 (PRIOR ART) is a diagram showing the commonly used criticaltemperature method after compensating for insignificant temperaturechanges in the control of fan rotational speed;

FIG. 3 is a block diagram showing the basic configuration of the systemfor control of fan rotational speed according to the present invention;

FIG. 4 is a flow chart showing the operational procedures which focuseson the low and high speed mode of fan rotational speed according to themethod for control of fan rotational speed of the present invention; and

FIG. 5 is a relevant diagram of the method for control of fan rotationalspeed of the present invention, showing how the fan rotational speedvaries with the critical temperature value, when progress the rotationalspeed control to the fan body.

DETAILED DESCRIPTION OF THE PREFFERED EMBODIMENTS

FIG. 3 is a block diagram showing the basic configuration of the systemfor control of fan rotational speed according to the present invention.As shown in the diagram, the fan rotational speed control system 3includes at very least: a temperature detecting module 30, a temperatureinterval recording module 31, a rotational speed recording module 32,and a determining module 33, wherein the system 3 is connected to a fanbody 4. The fan rotational speed control system 3 is implemented in theelectronic device which adjusts the system temperature through the useof the fan. In the example, the electronic device is a server computer,and the fan of the fan body 4 is controlled at a low and a highrotational speed.

The temperature detecting module 30 is used to detect the temperatureparameter of an exothermic object (e.g. a CPU, etc.) being adjusted bythe fan. In the example, the temperature detecting model 30 can betemperature detector, which is used to detect the system temperature inreal time when the server is operating and sends out the systemtemperature to the determining module 33.

The temperature interval recording module 31 is used to recordtemperature intervals related to different fan rotational speeds. Forexample, a preset critical temperature value Ct of 50° C. and aninsignificant temperature change Δt of 3° C. When the system temperatureis higher than 50° C., the fan rotational speed control system 3 willcontrol the fan body 4 to enter high speed operation, and when thesystem temperature is lower than 47° C. (i.e. the critical temperaturevalue Ct minus the insignificant temperature change Δt), the fanrotational speed control system will control the fan body 4 to enter lowspeed operation. In more detailed description, if the present fanrotational speed is in low speed mode, the critical temperature intervalshould be merged into the low rotational speed interval, and if thepresent fan rotational speed is in high speed mode, the criticaltemperature interval should be merged into the high rotational speedinterval.

The rotational speed recording module 32 is used to record the presentrotational speed when the fan is operating; the record provides animportant basis for the determining module 33 to make decisions.

The determining module 33 is used to determine the temperature intervalrelated to the present temperature parameter detected by the temperaturedetecting module 30. In the example, it executes the determinationaccording to the result defined by the temperature interval recordingmodule 31 previously mentioned. The decision of determining module 33 isbased on whether the present temperature parameter belongs to thetemperature interval recorded in the temperature interval recordingmodule 31. If yes, the fan body 4 will still operate with the presentrotational speed, i.e. keep the present rotational speed.

However, when the determining module 33 determines that the temperatureparameter does not belong to the temperature interval, then, accordingto the temperature parameter recorded in the temperature intervalrecording module 31, it determines whether the fan rotational speedrelated to the temperature parameter is the same as the fan rotationalspeed recorded in the rotational speed recording module 32. If, when thefan rotational speed is different, then, according to the temperatureparameter recorded in the temperature interval recording module 31, itdetermines whether the temperature parameter is lower than thetemperature interval. If the parameter is lower than the temperatureinterval, it reduces the rotational speed of the fan body 4, and, at thesame time, it updates the rotational speed module 32 with the reducedrotational speed. In contrast, when the temperature parameter determinedby the determining module is not lower than the temperature interval, itoperates the fan body 4 with the present rotational speed (i.e. keepsthe present rotational speed).

On contrary, when the determining module 33 determines the fanrotational speed related to the temperature parameter is the same as thefan rotational speed recorded in the rotational speed recording module32, then, according to the temperature parameter recorded in thetemperature interval recording module 31, it determines whether thetemperature parameter is higher than the temperature interval. If theparameter is higher than the temperature interval, it increases therotational speed of the fan body 4, and, at the same time, it updatesthe rotational speed module 32 with the increased rotational speed. Incontrast, when the temperature parameter determined by the determiningmodule is lower than the temperature interval, it operates the fan body4 with the present rotational speed (i.e. keeps the present rotationalspeed).

FIG. 4 is a flow chart showing the operational procedures focusing onthe low and high speed modes of fan rotational speed according to themethod for control of fan rotational speed of the present invention. Inorder for the electronic equipment, such as a server, to apply thesystem and the method for control of fan rotational speed of the presentinvention, the previously mentioned temperature interval recordingmodule 31 is created in advance in a memory unit, such as the BIOS ROM,for recording the relative first fan rotational speed (i.e. high speedmode) when the temperature is at least higher than a temperatureinterval (i.e. the interval between the critical temperature value Ctand the insignificant temperature change Δt), and the relative secondfan rotational speed (i.e. low speed mode) when the temperature is lowerthan the temperature interval.

First, in step S10, activate the fan body 4 during the operationalprocess of the server, and record the activated fan rotational speedinto the rotational speed recording module 32. In the example, the fanrotational speed is at the low rational speed. Next, execute step S11.

In step S11, make the temperature detecting module 30 detect thetemperature of the server when operating, and output the presenttemperature T. Next, execute step S12.

In step S12, make the determining module 33 determine whether thepresent fan rotational speed is in low speed mode. If yes, execute stepS13. If no, executes step S14.

In step S13, make the determining module 33 determine whether thepresent system temperature T is higher than the critical temperaturevalue, i.e. the preset critical temperature value 50° C. previouslydescribed. If not, execute step S15. Otherwise, execute step S16.

In step S14, make the determining module 33 determine whether thepresent system temperature is lower than the critical temperature valueminus the preset amount of insignificant temperature change (i.e. belowthe critical temperature value Ct of 50° C. minus the amountinsignificant temperature change Δt of 3° C. previously described, for alower limit of 47° C.). If yes (i.e., it is lower), execute step S17.Otherwise, execute step S18.

In step S15, keep the fan rotational speed the same and return to thepreviously described step S11. Repeat the execution of the step S11 tothe step 18, so that the fan rotational speed will be changed timelyaccording to the system temperature.

In step S16, make the determining module 33 adjust the rotational speedof the fan body 4 to the high rotational speed mode, and return to thepreviously described step S11. Repeat the execution of the step S11 tothe step 18, so that the fan rotational speed will be changed timelyaccording to the system temperature.

In the step S17, make the determining module 33 adjust the rotationalspeed of the fan body 4 to the low rotational speed mode, and return tothe previously described step S11. Repeat the execution of the step S11to the step 18, so that the fan rotational speed will be changed timelyaccording to the system temperature.

In the step S18, keep the fan rotational speed the same, and return tothe step S11. Repeat the execution of the step S11 to the step 18, sothat the fan rotational speed will be changed timely according to thesystem temperature.

FIG. 5 illustrates the result of the controlled rotational speed of thefan body 4 according to the method for control of fan rotational speedapplied in the present invention. In contrast with the prior art wheremore frequent abrupt changes occur as shown in FIG. 2, in the presentinvention, the temperature intervals can be adjusted by the system andthe method for control of fan rotational speed of the present inventionaccording to the fan rotational speeds. With the present invention,numerous abrupt changes of fan rotational speed caused by temperatureoscillations around can be avoided, the fan rotational speed can besmoothed, the life of the fan can be prolonged, and system noise can bereduced.

Moreover, the present invention is not only suitable for a two-speedfan, but also suits multiple critical temperature values. For instance,the temperature range of two critical temperature values Ct₁ and Ct₂(Ct₁ is smaller than the Ct₂) and the relative fan rotational speeds areslow speed mode, medium speed mode, and high speed mode. The adjustmentstoward the case are:

1. the fan rotational speed is kept unchanged when it is determined thatthe system temperature T is lower than the critical temperature valueCt₁ and the present fan rotational speed is in the low speed mode; thefan rotational speed is adjusted to the medium speed mode when it isdetermined that the system temperature T is higher than the criticaltemperature value Ct₁ and lower than the critical temperature value Ct₂;the fan rotational speed is adjusted to the high speed mode when it isdetermined that the system temperature T is higher than the criticalvalue Ct₂.

2. If the present fan rotational speed is at the medium speed mode, thefan rotational speed is adjusted to the low speed mode when the systemtemperature T is lower than the critical temperature value Ct₁ minus theamount of the insignificant temperature change Δt; the fan rotationalspeed is kept unchanged when the system temperature T is higher than thecritical temperature value Ct₁ minus the amount of the insignificanttemperature change Δt and, at the same time, lower than the criticaltemperature value Ct₂; the fan rotational speed is adjusted to the highspeed mode when the system temperature T is higher than the criticalvalue Ct₂.

3. If the present fan rotational speed is at the high speed mode, thefan rotational speed is adjusted to the low speed mode when the systemtemperature T is lower than the critical temperature value Ct₁; the fanrotational speed is adjusted to the medium speed mode when the systemtemperature T is higher than the critical temperature value Ct₁ andlower than the critical temperature value Ct₂ minus the amount of theinsignificant temperature change Δt; the fan rotational speed is keptunchanged when the system temperature T is higher than the criticaltemperature value Ct₂ minus the amount of the insignificant temperaturechange Δt.

A rotational speed control flow chart of relative multiple criticaltemperature values and more than three fan rotational speeds can be madeaccording to the adjustment scheme mentioned above. The flow chart canbe generated by making a few changes to the basic operational proceduresshown in FIG. 4, thus the adjustment scheme will not be furtherdescribed.

The embodiments described above are only to illustrate aspects of thepresent invention; they should not be construed as to limit the scope ofthe present invention in any way.

The invention has been described using exemplary preferred embodiments.However, it is to be understood that the scope of the invention is notlimited to the disclosed embodiments. On the contrary, it is intended tocover various modifications and similar arrangement. The scope of theclaims therefore should be accorded the broadest interpretation so as toencompass all such modifications and similar arrangements.

1. A system for control of fan rotational speed of a fan in anelectronic device for temperature adjustment, comprising: a temperatureinterval recording module for at least recording a first fan rotationalspeed of the fan when a temperature of the fan is higher than apredetermined temperature interval and a second fan rotational speed ofthe fan when the temperature of the fan is lower than the predeterminedtemperature interval; a rotational speed recording module for recordinga fan rotational speed of the fan during operation of the fan; atemperature detecting module for detecting a temperature of anexothermic object being adjusted by the fan and outputting a temperatureparameter; and a determining module for determining whether thetemperature parameter output by the temperature detecting module belongsto the temperature interval recorded by the temperature intervalrecording module, if yes, allowing the fan to operate at the same fanrotational speed, or if no, according to the temperature parameterdetermining from the temperature interval recording module whether a fanrotational speed corresponding to the temperature parameter is the sameas the fan rotational speed recorded by the rotational speed recordingmodule; if the fan rotational speeds are different, according to thetemperature parameter determining from the temperature intervalrecording module whether the temperature parameter is lower than thetemperature interval; if the temperature parameter is lower than thetemperature interval, reducing the fan rotational speed of the fan andupdating the fan rotational speed recorded by the rotational speedrecording module with the reduced fan rotational speed, or if thetemperature parameter is not lower than the temperature interval,allowing the fan to operate at the fan rotational speed recorded by therotational speed recording module; or if the fan rotational speeds arethe same, according to the temperature parameter determining from thetemperature interval recording module whether the temperature parameteris higher than the temperature interval; if the temperature parameter ishigher than the temperature interval, increasing the fan rotationalspeed of the fan and updating the fan rotational speed recorded by therotational speed recording module with the increased fan rotationalspeed, or if the temperature parameter is not higher than thetemperature interval, allowing the fan to operate at the fan rotationalspeed recorded by the rotational speed recording module.
 2. The systemas claimed in claim 1, wherein the temperature interval recorded by thetemperature interval recording module is formed by a criticaltemperature value and a small temperature difference from the criticaltemperature value.
 3. The system as claimed in claim 2, wherein thecritical temperature value serves as an upper limit of the temperatureinterval, and a lower limit of the temperature interval corresponds to avalue of the critical temperature value minus the small temperaturedifference.
 4. The system as claimed in claim 1, wherein the firstrotational speed is greater than the second rotational speed.
 5. Thesystem as claimed in claim 1, wherein the temperature interval recordingmodule is further for recording a plurality of temperature intervalscorresponding to different fan rotational speeds.
 6. A method forcontrol of fan rotational speed of a fan in an electronic device fortemperature adjustment, comprising the steps of: having the electronicdevice at least record a first fan rotational speed of the fan when atemperature of the fan is higher than a predetermined temperatureinterval and a second fan rotational speed of the fan when thetemperature of the fan is lower than the predetermined temperatureinterval, and record a fan rotational speed during operation of the fan;having the electronic device detect a temperature of an exothermicobject being adjusted by the fan and output a temperature parameter;having the electronic device determine whether the output temperatureparameter belongs to the recorded temperature interval, if yes, allowingthe fan to operate at the same fan rotational speed, or if no, accordingto the temperature parameter determining whether a fan rotational speedcorresponding to the temperature parameter is the same as the recordedfan rotational speed during operation of the fan; if the fan rotationalspeeds are different, according to the temperature parameter determiningwhether the temperature parameter is lower than the temperatureinterval; if the temperature parameter is lower than the temperatureinterval, reducing the fan rotational speed of the fan and updating thefan rotational speed recorded in the electronic device with the reducedfan rotational speed, or if the temperature parameter is not lower thanthe temperature interval, allowing the fan to operate at the fanrotational speed recorded in the electronic device; if the fanrotational speeds are the same, according to the temperature parameterdetermining whether the temperature parameter is higher than thetemperature interval; if the temperature parameter is higher than thetemperature interval, increasing the fan rotational speed of the fan andupdating the fan rotational speed recorded in the electronic device withthe increased fan rotational speed, or if the temperature parameter isnot higher than the temperature interval, allowing the fan to operate atthe fan rotational speed recorded in the electronic device.
 7. Themethod as claimed in claim 6, wherein the temperature interval recordedby the electronic device is formed by a critical temperature value and asmall temperature difference from the critical temperature value.
 8. Themethod as claimed in claim 7, wherein the critical temperature valueserves as an upper limit of the temperature interval, and a lower limitof the temperature interval corresponds to a value of the criticaltemperature value minus the small temperature difference.
 9. The methodas claimed in claim 6, wherein the first rotational speed is greaterthan the second rotational speed.
 10. The method as claimed in claim 6,wherein the electronic device further records a plurality of temperatureintervals corresponding to different fan rotational speeds.